Pickling restrainer and the manufacture thereof



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Patented Aug. 6, 1935 UNITED STATES PICHJNG ass'raamsa mm was MANUFACTURE THEREOF Deric Parkes,

Edgbaston. Birming England No Drawing.

Application January 16, 1033,

Serial No. 652,024. In Great Britain January This invention relates to the pickling of iron and steel and to the production 01 substances for use therein or for other purp ses.

It is well known that a number of substances serve, when added to pickling baths, to inhibit or restrain the dissolution or etching of the metals themselves, while allowing the removal oi the oxide or other skin or scale to proceed unhampered. Included among the substances which have hitherto been proposed are thiazole derivatives obtained by heating sulphur with. for example, o-toluidine. Organic bases containing in their molecule nitrogen rings, especially the quinoline nucleus, have also been proposed. The reason why these or any other substances exert their inhibiting or restraining action is not understood, and it is not possible to tell in advance whether any given substance will act as an inhibitor or restrainer at all or to any useful extent.

One object the present invention is to provide an improved restrainer. Another object is to provide a substance which can be employed in conjunction with acids and organic solvents for removing rust and grease from iron and steel prior to painting.

Another object will be eilective with is to provide a restrainer which any 0! the acids commonly employed for pickling iron and steel. 1n usual pickling practice sulphuric acid or hydrochloric acis is employed, but other acids, for example nitric acid and phosphoric acid, are sometimes used either alone or in conjunction with other acids ior pickling special steels, such as stainless steel, or in order to give a finish which is suitable ior some particular subsequent treatment. for example galvanizingmwhereas the restrainers used hitherto are in some cases not eflective in all acids. especially nitric acid, the invention aims at providing a restrainer which shall be eiiectlve with all aci We have found that excellent restraining sub stances can be obtained by sulphurating a cyclic base having in the molecule at least one ring containing both carbon and nitrogen atoms and only such atoms in that ring and in which the carbon atoms are saturated with hydrogen or at least one hydrogen atom has been substituted by a hydrocarbon radical. The bases which it is preierred to use consist o! homologues of pyridine such as 'a-picoline and in particular the substances known in commerce as heavy pyridine bases. The piperidine bases corresponding to the above as well as piperidine itself are also articularly satisfactory. In addition dipiperi- (CL 14H) dyls and homologues of qulnoline may be employed. A mixture of such bases may be employed.

The sulphurated bases may also be used as ingredients in materials ior cleaning iron or steel 5 prior to painting.

The bases may be sulphurated by beating them with sulphur. This heating may take place at temperatures of 130 C. and upwards for a period varying from a few minutes up to 25 to 30 hours. With a given class of base the period of heating can be reduced as more sulphur is used. Different classes of bases, however, require different periods of heating; thus the reduced bases such as piperidines and dipiperidyls require only a 5 few minutes while the heavy pyridine bases require to hours. The temperature of heating varies with the boiling point of the bases under amospheric pressure, although by increasing the pressure bases of low boiling point may be heatgo ed at higher temperatures.

The bases may also be sulphurated by the action of sulphur monochloride. The action in this case is much more violent than with sulphur and can conveniently be modified by the use of 5 diluents such as benzene and paraifln hydrocarbon which do not react. The advantages of the use of sulphur chloride are that the duration of the reaction is considerably reduced, and no sulphurislostasinthecaseoiheating withsulo phur. about half or which is evolved as hydrogen sulphide.

The reaction products may be added directly to the pickling baths, but are preferably first dissolved in sulphm'ic acid, in which state they may be purified. For this purpose they may be heated to about 105 C. to 120 C. and simultaneously blown with steam. The products obtained may either be added to the pickling baths alone or they may be mixed with a irothing agent, tor ex- 40 ample glue, sulphite cellulose waste liquor, casein, sine and the like. or, when used in conjunction with acids for removing rust and grease from iron and steel. they may be mixed with organic solvents. when used in coniimction with a irothing agent the restraining action of the product is not increased, but the irothing agent has the advantage that it renders the removal of dirt from the work easier when this is taken from the bath, and in addition the froth decreases to the nuisance of acid spray.

The following is an example of the manner in which the restraining substances in accordance with the invention may be produced and employed in pickling baths for iron and steel.

A quantity of the product known in commerce as heavy pyridine bases, having a specific gravity 01' 0.971 at 15 C. and distilling at temperatures "between 155 and 205"C.is introduced into a Still fitted with a reflux condenser together with 4 pounds of dry commercial sulphur to each gallon of the heavy pyridine bases introduced. The mixture is heated until there is a gentle reflux from the condenser. The temperature of the liquid at this stage is about 135 0., hydrogen sulphide is evolved, and the heating is continued for about 20 to 25 hours, when the temperature of the liquid will have risen to about 155 C. The product, which amounts in volume to about of a gallon to each 1 gallon of heavy Py dine bases employed, and of which the specific gravity is about 1.164, is then allowed to cool. The sulphurated bases thus prepared may be added in this form to the pickling bath, but preferably they are mixed with an equal volume of sulphuric acid Sp. Gr. 1.45, care being taken to prevent undue rise in temperature. Scum and tarry matter then rise to the surface and are separated by any convenient method. However, the sulphate of the sulphurated bases still contains impurities having an oiiensive odour, and to remove these the liquid is heated to a temperature of from 105 to 120 C. and simultaneously blown with steam. On cooling. the product is rehdy'ior use with or without dilution or for mixiiigwith irothing agents. To produce a non-fro restrainer the said product is mixed with an equal volume of sulphuric acid of Sp. Gr. 1.45. This mixture when added in a concentration of 0.02% by volume to a pickling bath containing 4% of sulphuric acid gives with mild steel at 90 C. a restraint of 80% as measured by the percentage drop in the hydrogen evolution in comparison with the hydrogen evolution without the addition of a restrainer. By adding a greater quantity of the restrainer the degree oi restraint may be increased.

To produce a irothing restrainer the product may, for example, be mixed with an equal volume of sulphuric acid Sp. Gr. 1.45 containing 3 to 6% of casein, glue, or other suitable irothing agent, and is then added to the pickling bath in a small percent by volume.

As previously mentioned, the sulphurated product obtained from the reaction may be added in small quantity directly to the pickling bath.

For treating iron or steel prior .to painting the sulphurated base obtained is added together with one or more organic solvents to an acid such as phosphoric acid. For example, a suitable material is made as iollows:-'-

To 12.94 gallons of phosphoric acid Sp. Gr. 1.75 there is added 1 gallon of sulphurated base, 3 gallons or furfural and 3 gallons of industrial spirit. The whole is then diluted with water to produce 100 gallons of finished product. v

We claim:

1. In the pickling or iron or steel the step which comprises adding to the pickling bath a product obtained by heating with sulphur one or more of the substances contained in the group comprising piperidine or its homologues, homologues of pyridine, dipiperidyls, and homologues of quinoline.

2. In the pickling of iron or steel the step which comprises adding to the pickling bath a product obtained by treating with sulphur chloride one or more of the substances contained in the group comprising piperidine or its homologues, homologues of pyridine, dipiperidyls, and homologues of quinoline.

3. In the cleaning of iron or steel prior to painting the step which comprises subjecting the surface to be cleaned to the action of a material comprising an acid, at least one organic solvent, and a product obtained by sulphurating at least one o! the substances contained in the group comprising piperidine, homologues of piperidine, homologues of pyridine, dipiperidyls, and homologues of quinoline.

4. In the pickling of iron or steel, the step which comprises adding to the pickling bath a product obtained by sulphurating at least one of the substances contained in the group comprising piperidine, homologues of piperidine, homologues of pyridine, dipiperidyls and homologues of quinoline.

DERIC WIILIAM PARKES. CHARLES DONALD MITCHELL. 

